1. Technical Field
An additive for a photoresist composition for a resist flow process, and a photoresist composition comprising the same are disclosed. In particular, a photoresist composition comprising an additive which lowers the glass transition temperature of the photoresist polymer, and a method for forming a contact hole using the same are disclosed.
2. Description of the Background Art
Recently, semiconductor devices have been highly integrated. It is difficult to form a contact hole having a high resolution in lithography process. Currently, a contact hole patterning limit of KrF lithography is about 0.18 xcexcm. Resist flow is a processing technology for forming a fine contact hole which exceeds the resolution of the exposing device.
The resist flow process has recently made remarkable developments and so that it is now used in mass production processes. The technology generally involves an exposure process and a development process. This process forms a photoresist contact hole having a resolution equal to that of the exposing device. The process also includes heating the photoresist to a temperature higher than the glass transition temperature of the photoresist which causes the photoresist to flow. The contact hole gets smaller by the flow of photoresist until a fine contact hole necessary for the integration process is obtained.
Most of the KrF resists can be flow processed, though having different profiles after the flow process. That is, the KrF resist mainly containing polyvinylphenol consists of a structure having appropriate Tg for the flow. However, a resist used for ArF lithography has so high Tg that it cannot be flow processed. Especially, cycloolefine resists have a Tg over about 200xc2x0 C., and thus is not suitable for the resist flow process. An appropriate temperature for the resist flow process ranges between the Tg of the photoresist polymer and a decomposition temperature (Td) where the polymer starts to be decomposed. Therefore, the polymer having high Tg cannot be used for a resist flow because the Tg and Td have only a slight difference. Therefore, there is a need for a modified resist material with a suitable disparity between the Tg and Td thereby making it suitable for resist flow processing.
An additive for a photoresist composition thereby making it suitable for a resist flow process is disclosed.
Photoresist compositions comprising such additive for a resist flow process are also disclosed.
A resist flow process for forming a photoresist pattern using such photoresist composition is also disclosed.
A contact hole formation method employing the photoresist pattern formed by the above-described process is also disclosed.